Catalytic reforming of mixed gasolines



Sept. 23, 1947. W. J. MATTox CATALYTIQ REFORMING OF MIXED'GASOLINESFiled March s1, 1945 Patented Sept. 23, 1947 CATALY'I'IC REFORMING MIXEDGASOLINES William J. Mattox, La Grange, Ill., assigner to Universal OilProducts Company, Chicago, Ill., a corporation of Delaware ApplicationMarch 31, 1945, Serial No. 585,999

This invention relates to the catalytic reforming of gasoline fractionsand is more particularly concerned with the reforming of a mixture ofspecific fractions of straight run gasoline and thermally crackedgasoline under selective conditions of operation.

In the past, considerable work has been done on the reforming ofgasoline fractions primarily y to improve their antiknock properties bythe dehydrogenation of naphthene hydrocarbons contained therein toaromatics and the dehydrocyclization of paraiinic hydrocarbons toaromatic hydrocarbons. Generally, in ythis known operation, the naphthafractions are subjected to contact with a reforming catalyst attemperatures within the range of from 400 C. to 600 C. and underpressures ranging from atmospheric to approXimatelyZO atmospheres.Naphtha fractions have also been reformed in an operation commonlycalled hydroforming inlwhich the naphtha is converted in the presence ofhydrogen under conditions of temperature and pressure similar to thosegiven above.

One of the chief difficulties of the previously described processeswhich has hampered the commercialization of these processes is thatafter relatively short periods of operation the catalyst tends to loseactivity as a result ofdeposition of carbonaceous materials thereon-When this occurs it becomes necessary to reactivate the catalyst byremoving the carbonaceous materials from the catalyst either bycombustion or some other means, Since the catalysts usually employed forthe reforming operation are somewhat thermophobic it is necessary toregulate the temperature rise obtained in the catalyst Zone by employinga regenerating gas composed of inert gas such as nitrogen and smallamounts of oxygen. This regeneration operation entails the use of largeand expensive equipment such as compressors, combustion gas generators,and so forth, which increases to a considerable extent the capital costof the operation and decreases the commercial attractiveness of theprocess.

Further, the necessity of frequent regeneration prevents the operationfrom being truly continuous and forces the adoption of complicatedschemes employing a plurality of reaction zones with staggered reactioncycles to provide a pseudo continuous operation. Here, again, theadoption of these complicated schemes increases the capital cost of theequipment.

It is a particular object of the present invention to provide acatalytic reforming process in Which the cafabfst may be employed forperiods 1 Claim. (Cl. 196--50) in excess of about 10-15 days without thenecessity of regeneration. This long on-stream time makes it possible todispense with the need of auxiliary equipment for the regeneration ofthe catalyst as an integral part of the process.

In a broad aspect the present invention provides a process forcatalytically reforming gasoline fractions which comprises subjecting amixture of a straight run gasoline fraction and a thermally crackedgasoline fraction, the former fraction comprising at least by volume ofsaid mixture and the latter fraction consisting primarily ofhydrocarbons boiling above C., to the action of a reforming catalyst inthe presence of hydrogen in the mol ratio of from about 0.5 mol to about15 mols of hydrogen per mol of hydrocarbon at a temperature Within therange of from about 400 C. to about 600 C. and under a pressure inexcess of about 30 atmospheres and correlating the conditions ofoperation and the proportions of the straight run gasoline fraction andcracked gasoline fraction to effect the reforming operation with no netconsumption of hydrogen. One of the essential features of the presentinvention is the fact that the operation is carried out with no netconsumption of hydrogen, The primary factors in maintaining thishydrogen balance within the process are the particular composition ofthe hydrocarbon feed and the operating conditions employed. In athermally cracked gasoline, a greater proportion of the olenichydrocarbons are found in the lower boiling fraction, that is, afraction boiling below approximately 120 C. If these olefinichydrocarbons are present in the portion of the feed being processed theamount of hydrogen required in the operation will be lmateriallyincreased, thereby disrupting the balance between the hydrogen requiredfor saturation reactions and that produced in situ by dehydrogenationreactions and effect a net hydrogen consumption in the process.Therefore, to maintain a continuous operation it would be necessary tocontinuously supply hydrogen from some extraneous source which wouldresult in a substantial increase in the cost of the operation anddestroy its commercial utility. If, however, selected fractions of thecracked gasoline are employed, that is, those containing hydrocarbonsboiling above 120 C. the percentage of olens present is much lower.These fractions contain substantial quantities of naphthenichydrocarbons which upon dehydrogenation form aromatic hydrocarbons andthereby provide a source of hydrogen. This hydrogen production issufficient to furnish at least a portion of the hydrogen consumed in thehydrogenation of hydrocarbon fragments produced by decompositionreactions. By a careful selection of the fractions of straight run andcracked gasolines employed and the proportions thereof, all the hydrogenneeded for these hydrogenation reactions can be produced in situ thuspreventing carbon deposition, and dispensing with the necessity ofmaintaining an extraneous supply of hydrogen. Therefore, ideal chargingstocks for the process comprise straight run and cracked gasolinefractions having a high concentration of naphthenes which upondehydrogenation to the corresponding aromatics produce substantialquantities of hydrogen.

However, in considering the boiling range of the straight run gasolinefraction to be employed, it is usually advantageous to include the lowerboiling fractions thereof since the hydrocarbons contained thereinprovide a potential source of hydrogen.

As will be noted by studying the examples presented hereinafter in thisspecification, the operating conditions of temperature, pressure, and soforth, and the boiling ranges and proportions of the straight rungasoline and cracked gasoline fractions are selected so that nalgasoline blend including the reformed product and the materialoriginally removed from the gasoline prior to processing has a brominenumber substantially the same as that of a blend of the originalstraight run and cracked gasolines, that is within about 5 to 8 numbersthereof.

The catalyst which may be employed in the process of the presentinvention comprises compounds of the elements in the left-hand columnsof groups V and VI of the periodic table and in particular the oxides orsuldes of such elements as vanadium, chromium, molybdenum and tungsten,either alone or in admixture with one another. A particularly goodcombination comprises a mixture of the oxides of chromium andmolybdenum. While these compounds may be employed alone it is preferablethat they be used in conjunction with refractory supporting materialssuch as alumina, particularly activated alumina of commerce, silica,silica-alumina cornposites, magnesium oxide, zinc oxide, zirconiumoxide, titanium oxide, thorium oxide, acid-treated clays such asacid-treated montmorillonite or bentonite, and similar supportingmaterials.

The above catalyst may be prepared by various methods. For example, thesolid particles of the refractory material such as activated alumina maybe impregnated with solutions of soluble compounds of one or more of thevarious elements named above, the impregnated material beingsubsequently dried and calcined. The catalysts may also be prepared byprecipitation of a supporting material such as alumina in the presenceof a dissolved compound of, for example, chromium or molybdenum followedby evaporation of the solution and by drying and further heating of theresidue to develop the catalytic properties of the composite. Suitablecatalyst may also be prepared by co-precipitation of the supportingmaterials and the activating compound or compounds and the subsequentdrying and calcining of the precipitate. Another and particularlyapplicable method of catalyst preparation comprises the impregnation offreshly precipitated gels of the supporting materials such as alumina orsilica with at least one of the compounds furnishing the highlycatalytic component of the final catalyst followed by 'drying 4 andcalcining of the impregnated gel. If a metal oxide is the desiredcatalytic component, it may be obtained by impregnation of the drysuppo1't' ing material, or the gel respectively, with a decomposablecompound of the particular metal employed which produces an oxide uponcalcination. The concentration of the catalytic compound in the nalcomposite catalyst will vary depending upon the specific supportingmaterials and active compounds employed.

The various features of the present invention will be more clearlypointed out in the description of the attached drawing which illustratesin conventional side elevation one type of apparatus in which theprocess of the present invention may be performed. However, since thisdrawing is merely for illustrative purposes the following descriptionwith reference to this drawing is not intended to unduly limit the scopeof the invention.

A thermally cracked gasoline is introduced through line I containingvalve 2 into pump 3 which discharges through line 4 containing valve 5into fractionator 6 wherein the lighter materials are separated from thehigher boiling materials leaving a bottoms fraction having an initialboiling point of about 120 C. A straight run gasoline is introducedthrough line 9 containing valve I0 and is mixed in line 9 with thebottoms fraction withdrawn from fractionator 6 through line 'Icontaining valve 8, The mixture is directed into pump I I whichdischarges through line I2 containing valve I3 through heat exchanger I4into heating coil I5. The particular proportions of straight rungasoline and the higher boiling portion of the cracked gasoline may varysome what depending upon types of gasoline and the conditions oftemperature and pressure employed in reactor I8, but under nocircumstances will the amount of cracked gasoline be greater than about50% by volume of the mixture. The proportions will be regulated so thatno hydrogen consumption results in the operation. The mixed charge ispassed through heating coil I5, disposed within heater 'II, wherein itis heated to a temperature within the range of from about 400 C. toabout 600 C., and is introduced through line I5 containing valve I'Iinto reactor I8 wherein it is commingled with hydrogen or a hydrogencontaining gas obtained as hereinafter set forth.

Reactor I8 comprises a large cylindrical vessel containing therein solidparticles of catalyst in fixed bed relationship to the incomingreactants. The catalyst may be employed in large granules of varyingsize or may be of uniform size and shape such as pellets and extrudedpieces. 'I'he reaction zone I8 is maintained at a temperature within therange of from 400 to about 600 C. and under a pressure in excess ofabout 30 atmospheres. The hydrogen concentration within the reactionzone is regulated so that the mol ratio of hydrogen to hydrocarbon iswithin the range of about 0.521 to 15:1. The hydrocarbon charge rate tothe reactor is such that a liquid hourly space velocity within the rangeof about 0.1 to about 10 volumes of hydrocarbon charge per volume ofcatalyst and a mass velocity of the hydrocarbons in excess of 5milligrams per square centimeter per second are maintained.

Although the present description is limited to an operation in which thecatalyst is employed in a fixed bed relationship to the incomingreactants the operation may be conducted in various other ways. Forexample, the reactants may be introduced into the lower section of areaction zone containing finely divided catalyst and the reactantspassed upwardly at a rate suiicient to maintain the catalyst mass in afluidized condition, In this Inode of operation the reaction productsmay be removed from the upper portion of the reaction zone and passedthrough cyclone separators wherein any entrained catalyst is removed andthereafter into a fractionator wherein the desired products areseparated. The entrained catalyst removed in the cyclone separator maybe returned to the reaction zone.

Another method of operation consists of passing the hydrocarbonreactants and hydrogen either countercurrently or concurrently through adense moving mass of catalyst, the catalyst being continuously recycledto the reaction zone and the reaction products continuously removed fromthe reacting system.

Still another method of operation comprises adding nely divided catalystto the hydrocarbon charge mixing hydrogen or hydrogen containing gaseswith the charge, passing the entire mixture, wherein the catalyst isbeing maintained in suspension, through a heating zone maintained underthe desired conditions of temperature and pressure, separating thecatalyst from the hydrocarbon in a separating and fractionating zone andrecycling the catalyst to the reaction zone.

The products from reactor I8 are withdrawn through line I9 containingvalve 2U and are passed through heat exchanger i4 and line 2I containingvalve 22 into cooler 23 wherein the temperature of the reaction productsis substantially reduced. The cooled reaction products leave cooler 23through line 24, valve 25 and are introduced into receiver 26 whereinthe light gases rich in hydrogen are separated from the reactionproducts. Receiver 26 is maintained at slightly less pressure thanreactor I8. The gases separated from receiver 26 are withdrawn throughline 21, valve 28 into the suction of compressor 29 which dischargesthrough line 30, valve 3I into heating coil 32 disposed within heater1I. The hydrogen-containing gas may be heated to about the sametemperature to which the hydrocarbon charge is heated, or it may beheated to a temperature somewhat higher than that of the hydrocarboncharge, and is introduced to reactor I8 through line 33 containing valve34. The liquid products from receiver 26 are directed through line 35containing a pressure reducing valve 35 into receiver 31 which ismaintained at a pressure substantially lower than that of receiver 26.In receiver 31 additional separation of the light gases from the liquidhydrocarbons is effected, the light gases being removed through line 38containing valve 39 and directed intoabsorber 12 wherein small amountsof gasoline entrained in the gases are recovered.

A portion of the liquid hydrocarbons withdrawn from receiver 31 throughline 4D is directed through line 50 and valve 5I to the suction side ofpump 52 whichdischarges through line 53 containing valve 54 into line 2Ithereby effecting the recirculation of liquid hydrocarbons to receiver25. The recirculation of a portion of the liquid hydrocarbons to thisreceiver provides an additional solvent for the light hydrocarbon gasesin the reaction products from reactor I8, thereby effecting a morecomplete concentration of the hydrogen in the gases leaving receiver 26through line 21 and preventing the light hydrocarbon gases fromaccumulating in the recycle gas stream. The remaining portion of theliquid products withdrawn through line 40 is directed through valve 4Iinto heat exchanger 13 wherein the temperature is raised slightly andthe heated material passed through line 14 containing valve 15 intoreceiver 42. light gases is removed from the liquid products in receiverI42 and withdrawn through line 64 containing valve 65 into line 38wherein the gases are admixed with the gases from receiver 31 and themixture is introduced into absorber 12 to recover any entrained gasolinecontained therein.

The liquid product from receiver 42 is withdrawn through line 43containing valve 44 and commingled with the light hydrocarbons separatedfrom the `thermally cracked gasoline in fractionator 6, the latterhydrocarbons passing through line 56 containing valve 61 into pump 68which discharges through line E9 containing valve 1U into line 43. Themixture is directed through line 43 into stabilizer 45 whereinstabilization is effected to produce the desired vapor pressure in thefinal product. Butane from an external source may be added to thehydrocarbons in stabilizer 45 if necessary to produce the desired vaporpressure. The nal gasoline productr is withdrawn from stabilizer 45through line 46 containing valve 41. The light gases are withdrawnthrough line 48 containing valve 49 and may be cooled and collected asthe product of the reaction or may be used or withdrawn as fuel.

The lean oil employed in absorber 1.2 is introduced through line 59containing valve B into pump 5I which discharges through line 62containing valve 53 into the upper portion of the absorber. The rich oilcontaining gasoline absorbed therein, is withdrawn through line 51,valve 58 to any suitable recovery system. The unabsorbed gases areremoved through line 55 containing valve 56 and may be cooled andcollected as a product of the reaction or passed directly to the fuelsystem. The initial charge of hydrogen is introduced in the systemthrough line 13' containing valve 14. Hydrogen is introduced from anexternal source only during the initial starting of the operation sincethe process when conducted in accordance with the present inventionproduces sufcient hydrogen to maintain a balance during the remainingperiod of the operation.

If desired, the use of extraneous hydrogen may be avoided entirely. Theplant may be pressured with a suitable gaseous hydrocarbon fraction suchas a methane-containing fraction from natural gas or a hydrocarbon gasfraction derived from a thermal or catalytic cracking operation. Asubstantiallyv saturated hydrocarbon fraction containing substantialquantities of cyclohexane or alkyl cyclohexanes, preferably a fractionof this character derived from a straight run gasoline, is mixed withtheV gas and passed through the reaction zone under mild conditions toeiect dehydrogenation of the naphthenes to corresponding aromaticswithout substantial decomposition or carbon deposition. This treatmentof the naphthenic fraction is continued for a suflicient time to obtaina quantity of hydrogen adequate to supply the initial charge of hydrogenfor the reforming treatment. The hydrogen thus produced is separated andrecycled to the reaction Zone which, upon production of the hydrogen inadequate quantity, can then be employed to effect the catalyticreforming of the mixture of straight run and thermally cracked gasolinefractions.

An additional quantity of EXAMPLE I A 37.4 ASTM octane number straightrun naphtha was reformed in admixture with Various portions of a 65.3ASTM octane number cracked distillate over an alumina-chromium oxidecatalyst. The operating conditions in these tests were maintained asfollows:

Temperature C 500 Pressure atmospheres-- 68 Liquid hourly space velocity4 Hydrogen to hydrocarbon mol ratio 4:1

Forv comparative purposes an initial run was made on a mixturecontaining the total cracked distillate with an equal volume of straightrun and in test 6 a straight run gasoline only was reformed and blendedwith the untreated cracked distillate. The data obtained in this seriesof tests are summarized in Table I.

INSPECTION OF THE BLENDED GASOLINES Base Product charge,

Octane number, A. S. T. M. motor method. 73. 4 58. 4 +1 ce. TEL 80. 768. 5 +3 ce. TEL 84. 7 75. 6 Research octane number- 80. 4 63. 2 l ce.TE S7. 6 73. 0 +3 ce. TEL 91. 6 so. 1 Bromine number 33 Initial boilingpoint. 1

1 hase charge-50: 50 blend of original full boiling range cracked andstraight run gasolinas.

Table I Test No 1 2 3 4 5 6 Cracked Naphtha:

Vol. per cent removed 12.4 23. 3 .4 49. 9 100 I. B. P. of the remainingfraction, C Total 46 75 100 125 0 Vol. per cent reformed 100 81.6 76. 765. 6 50.1 0 Cracked Gasoline, vol. per cent in chg 43. 8 34. 4 32.8 25.1 0 St. Run, Vol. per cent in chg 50 50 50 50 50 100 Bromine No. ofblend 31 Recovery:

Liquid, vol. per cent 89. 8 91.0 92. 7 91. o 94. 2 91. o Liquid, Wt. percent 87. 8 89Y 0 90. 8 90.2 92. s so. 3 Gas, Uneond. wt. per cent. 11.09, 2 9. 8 7, 7 10. 2 Hydrogen Balance 1 0. 065 -0. 094 -0. 028 +0. 037+0.190 Overall Liq. Yield, Product and original fraction removed,

Vol. per cent 89- S 91.6 03. 5 91.9 95.6 95. 5 Analysis:

Motor Method clear 70. 5 68.0 69. 6 65. 8 66. 3 63. 8 Motor Method-H ce.TEL 2 79. 3 77. 9 77.8 76.8 76. 9 72. 8 Motor Method-F3 cc. TEL A 85.1S3. 1 83.7 82. 5 8l. 7 79. 7 Research Method clear 75. 6 73.7 75.1 73.073.3 70, 7 Research Method-H cc. TEL 81. 1 81.0 82. 5 80.5 80.8 78. 7Research Method+3 cc. TEL 89.1 87.1 88. 7 87. 9 87.1 84. 9 Reid VaporPressure 9. 9 6. 9 e. 9 5. 6 7. 2 5. 1 Bromine Number 4 1l 17 22 27 37Engler Distillation:

I. B. P 99 101 103 103 10S 115 129 135 134 138 145 152 173 234 282 318 l358 B77 407 1.2 0.3 54.1 0. 7624 l Moles Hz per mole naphtha feed. -l-Denotes hydrogen production; denotes hydrogen consumption.

2 Tetra Ethyl Lead.

EXAMPLE II A mixture of a straight run gasoline and the 300 to 400 F.fraction of a thermally cracked gasoline Was reformed under thefollowing conditions:

Catalyst Alumina-chromium oxide Temperature 520 C. Pressure 1000 lbs/sq.in. gauge Hydrogen recycle-- 4 moles/mole of hydrocarbon Mixturecomposition:

Straight run. vol. percent 73.6 (i300-400 F.) thermally crackedgasoline, vol. percent 26.4

The yields and comparison of the product with the base charge are shownin Table II.

Table II Yield of liquid product,V (Reformed product -|.-initial300 F.fraction of thermally cracked gasoline) 90.4 Hz produced, cu. ftJbbl. ofstraight run 47.5

It will be noted that though an appreciable improvement in the antiknockproperties is obtained in the operation, the bromine number of the finalblend is the same as that of the 50/50 blend of the original straightrun and cracked gasoline.

In the runs shown in Tables I and II, the operations Were continued fora period of 15 days with no substantial carbon deposition on thecatalyst. The properties of the product remained substantially constantthroughout the operation.

I claim as my invention:

A catalytic reforming process which comprises subjecting a mixture of astraight-run gasoline fraction and a thermally cracked gasolinefraction, the former fraction comprising at least 50 percent of thetotal mixture and the latter fraction consisting primarily ofhydrocarbons boiling above C., to the action of a reforming catalystdisposed Within a reaction zone in the presence of hydrogen in a molratio of about 0.5 mols 9 to about 15 mois of hydrogen per m01 ofhydrocarbon at a temperature within the range of about 400 C. to about600 C. under a pressure in excess of about 30 atmospheres, introducingthe cooled reaction products into a first separating zone and thereinseparating a gaseous mixture rich in hydrogen from liquid hydrocarbons,recycling said gaseous mixture to the reaction zone, introducing theliquid hydrocarbons from said rst separating zone into a secondseparating zone maintained at a substantially lower pressure than saidfirst separating zone and therein effecting further separation of gasescontaining hydrogen from liquid hydrocarbons, withdrawing a portion ofthe liquid hydrocarbons from said second separating zone and recyclingsaid portion to the rst separating zone, withdrawing the remainingportion of liquid hydrocarbons from said second separating zone, heatingsaid remaining portion and introducing the 20 Number heated hydrocarbonsinto a. third separating zone wherein light gases are separated from theliq- 10 uid hydrocarbons, introducing the light gases from said secondand third separating Zones into an absorber wherein small amounts ofgasoline hydrocarbons entrained in said light gases are recovered andstabilizing the liquid hydrocarbons Withdrawn from said third separatingzone.

WILLIAM J. MA'I'I'OX.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,335,717 Welty, Jr., et al. Nov.30, 1943 2,400,363 Meier May 14, 1946 FOREIGN PATENTS Country Date420,235 Great Britain Nov. 28, 1934 423,001 Great Britain Jan, 23, 1935

